This invention relates to a toroidal traction drive and, particularly, to such a mechanical drive whereby a control system may vary the drive ratio and, if desired, control the drive ratio whereby variable input speeds give a constant output speed from the drive.
Early work in the field of toroidal traction drives is shown in the Hayes U.S. Pat. Nos. 1,865,102 and 2,123,006. The patents describe the action of rollers between discs having annular grooves whereby tangential shift of the rollers results in rocking or precessing of the rollers to vary the drive ratio.
More recently, there has been published material with respect to a toroidal traction drive wherein a plurality of rollers are positioned between discs and with each roller mounted in a carrier. All the carriers are connected to a movable cam ring whereby movement of the cam ring causes movement of the rollers to vary the drive ratio. In such a device, all of the rollers are caused to be positioned through a common mechanical structure and, therefore, the positioning is subject to variations in the components of the mechanical structure.
The Magill et al. U.S. Pat. No. 3,413,864 discloses a toroidal traction drive wherein a plurality of drive rollers are each independently mounted and with hydraulic control means associated with each drive roller and acting on the roller in a manner to cause rocking of the drive rollers to vary the drive ratio.
An additional prior art patent is Armstrong U.S. Pat. No. 3,345,882 which discloses a toroidal traction drive wherein a plurality of drive rollers spaced between discs has fluid-operating devices associated with both ends of the roller mountings.